The primary objective of this multicenter study is to compare the safety, tolerability and efficacy of sb-204269 w/placebo as add-on therapy in patients with refractory simple or complex paritial seizure (with or without secondarily generalization). another objective is to gather population pharmacokinetic for sb-204269 as adjunct therapy in patients. the patient must have simple (with motor component) or complex partial seizures with or without secondarily generalization.